1. Field of the Invention
The invention pertains to a method for testing vibration dampers in motor vehicles wherein a parameter which corresponds to the damping force of a vibration damper is stored in a memory unit, and a vibration damper and wheel are subjected to a reciprocating excitation which is used to generate a parameter which is compared to the stored parameter to ascertain the condition of the vibration damper.
2. Description of the Related Art
A vibration damper is one of the parts of a motor vehicle which is subject to wear. It must be remembered that a defective vibration damper has a significant effect on the driving safety of the vehicle. The driver himself cannot verify the functionality of a vibration damper, because the damping behavior deteriorates gradually, and the driver becomes accustomed to it.
Certainly the best way to test the functionality of a vibration damper is to remove the vibration damper from the vehicle and to subject it to a testing program in a special test machine. This approach is described in DE 41 20 169 A1. When a spring strut unit is involved, however, with a suspension spring surrounding the vibration damper, it can be quite expensive to remove the vibration damper from the vehicle.
For this reason there have been numerous attempts to test a vibration damper for its functionality while it is still installed in the vehicle. The basic principle is to use a testing device with a drive unit which causes a wheel support plate to oscillate. A possible defect in the installed vibration damper can be detected by comparing its decay curve with that of a new vibration damper. U.S. Pat. No. 5,665,901, for example, describes a test bench of this type.
An essential problem, however, is that not only the vibration damper but also the axle joints and the vehicle tires play a part in the testing of the vibration damper. The influence of the vehicle tires can be minimized through the use of an elastic member in the test bench. This situation is presented in U.S. Pat. No. 6,531,958.